Various surgical methods employing sutures have been used in the past for closing or binding together wounds in human or animal tissue, such as skin, muscles, tendons, internal organs, nerves, blood vessels, and the like. More specifically, the surgeon may use a surgical needle with an attached conventional suture (which can be a smooth monofilament or can be a multi-filament) to pierce the tissue alternately on opposing faces of the wound and thus sew the wound closed. Whether the wound is accidental or surgical, loop stitching is the method often used, especially for surface wounds. The surgical needle is then removed and the ends of the suture are tied, typically with at least three overhand throws to form a knot.
As is well known, conventional sutures can be of non-absorbable material such as silk, nylon, polyester, polypropylene, or cotton, or can be of bio-absorbable material such as glycolic acid polymers and copolymers or lactic acid polymers and copolymers.
Since the time of their conception, barbed sutures, which are generally of the same materials as conventional sutures, have offered numerous advantages over closing wounds with conventional sutures. A barbed suture includes an elongated body that has one or more spaced barbs, which project from the body surface along the body length. The barbs are arranged to allow passage of the barbed suture in one direction through tissue but resist movement of the barbed suture in the opposite direction. Thus, the main advantage of barbed sutures has been the provision of a non-slip attribute. Accordingly, barbed sutures do not have to be knotted, like conventional sutures. Like a conventional suture, a barbed suture may be inserted into tissue using a surgical needle.
For instance, U.S. Pat. No. 3,123,077 to Alcamo describes an elongated cord for sewing human flesh, where the cord has a body portion and sharp-edged, resilient barbs projecting from the body at acute angles relative to the body. The barbed suture can be passed through tissue in one direction, but resists movement in the opposite direction.
Sutures with barbs disposed in a bi-directional arrangement, also called double-armed sutures, are shown in U.S. Pat. No. 5,931,855 to Buncke and U.S. Pat. No. 6,241,747 to Ruff. More particularly, the suture has barbs facing toward one end of the suture for about half the suture length and barbs facing in the opposite direction toward the other end of the suture for the other half of the suture length. This arrangement allows the barbs to move in the same direction as each respective suture end is inserted into the first and second sides of a wound. Such bi-directional barbed sutures not only are especially suitable for closing wounds with edges prone to separation, but also obviate the need to secure suture ends together with knotted loops.
Of interest is European Published Patent Application No. 1,075,843 A1 to Sulamanidze and Mikhailov, published Feb. 2, 2001, derived from PCT/RU99/00263 (published as WO 00/51658 on Sep. 8, 2000), priority to RU 99103732 (Mar. 3, 1999), which shows conical barbs arranged sequentially along the length of a thread and oriented in a direction opposite to that of the thread tension, with the distance between barbs being not less than 1.5 times the thread diameter.
Also of interest is U.S. Pat. No. 5,342,376 to Ruff. This patent shows an insertion device that is useful for positioning a barbed suture in order to close a wound. The insertion device has a tubular body for receiving a barbed suture, and preferably also has a handle to facilitate manipulation of the device by the surgeon. The insertion device is recommended for use with a barbed suture where the suture portion being inserted includes barbs facing a direction opposed to the direction of insertion. Such sutures with barbs opposing the direction of insertion are also shown in '376 to Ruff.
The disclosures of all patents and patent applications mentioned here are incorporated by reference.
Escarpment of barbs into a monofilament, depending on the barb cut depth, reduces the straight pull tensile strength since the effective suture diameter is decreased. However, the straight pull tensile strength of a barbed suture should be compared to the minimum knot pull strength of a conventional suture (a non-barbed suture) in accordance with the United States Pharmacopoeia since failure of conventional sutures (which have to be knotted and must meet a minimum knot pull tensile strength) occurs most frequently at the knot due to increased local stress.
To optimize the performance of a barbed suture, it is advantageous to consider varying the barb geometry (barb cut angle, barb cut depth, barb cut length, barb cut distance, etc.) and/or the spatial arrangement of the barbs. This should not only enhance the tensile strength of a barbed suture, but also should enhance the ability of a barbed suture in holding and maintaining wound edges together. Unlike conventional sutures, which place tensions directly at the knots, barbed sutures can spread out the tension along the escarped suture length, often evenly along the length. Optimizing the disposition and/or the configuration of the barbs should therefore further increase the effectiveness of the new barbed suture in maximizing the holding strength and minimizing the gap formation along the wound edges. The latter is particularly beneficial for promoting wound healing.
Also, such new barbed sutures should approximate tissue quickly with appropriate tension, alleviate distortion of tissue, and help to minimize scarring, due to the self-retaining benefits imparted by the barbs. The new barbed sutures would be especially useful in surgeries where minimization of scarring is imperative, such as cosmetic surgery, as well as in surgeries where space is limited, such as endoscopic surgery or microsurgery.